The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to a conveyor, which comprises a frame, an endless conveyor belt supported by the frame and driven by driving means in a conveying direction along a helical path, a non-helical path and a transfer path extending between the helical path and the non-helical path, wherein the helical path has an upright center line, and wherein the conveyor belt includes a plurality of plates which are movably coupled to each other and each plate having an upper transport face and a central axis.
Such a conveyor is known from U.S. Pat. No. 5,413,213 or U.S. Pat. No. 5,490,589. The endless conveyor belt of the known conveyor follows an outer helical path upwardly, after which it leaves the outer helical path via a transfer path to an S-shaped path which is coupled to an inner helical path along which the conveyor belt is guided downwardly. A disadvantage of the known conveyor is that the conveyor belt is not guided stable enough between the helical path and the S-shaped path. In order to keep the conveyor belt on track a relatively high tension force on the conveyor belt is required. This is, however, disadvantageous in terms of friction between the conveyor belt and the frame. A radial guide of relatively large height might seem a possible solution, but this is undesired since a large construction height of the conveyor belt makes it difficult to guide the conveyor belt about reversing wheels. Besides, a large construction height limits vertical space between two neighboring helical windings.